Ribonucleotide reductase catalyzes the rate-limiting step in the de novo synthesis of 2'-deoxyribonucleoside 5'-triphosphates that is required for DNA replication. The mammalian enzyme consists of two nonidentical protein subunits that are both required for enzyme activity. In leukemia L1210 cells, enriched in G1-phase cells by centrifugal elutriation, it was found that ribonucleotide reductase...

The aim of this experimental study was to investigate the mechanism by which nicotine (NIC) alters spermatozoa and to evaluate the expression of nicotinic receptors (nAChR) subunits in human spermatozoa. We analyzed 30 healthy normozoospermic men. Spermatozoa were incubated with NIC 100 ng/ml and the nAChR antagonist, hexamethonium (HEX) (0, 100, 1,000, 10,000 ng/ml) for 3 and 24 h. The followi...

The voltage-gated K+ (Kv) channel subunits Kv2.1 and Kv2.2 are expressed in almost every tissue. The diversity of Kv2 current is increased by interacting with the electrically silent Kv (KvS) subunits Kv5-Kv6 and Kv8-Kv9, into functional heterotetrameric Kv2/KvS channels. These Kv2/KvS channels possess unique biophysical properties and display a more tissue-specific expression pattern, making t...

In vivo depletion of the yeast small ribosomal subunit (SSU) protein S5 (rpS5) leads to nuclear degradation of nascent SSUs and to a perturbed global assembly state of the SSU head domain. Here, we report that rpS5 plays an additional local role at the head/platform interface in efficient SSU maturation. We find that yeast small ribosomal subunits which incorporated an rpS5 variant lacking the ...

Cellular production of ribosomes involves the formation of highly defined interactions between ribosomal proteins (r-proteins) and ribosomal RNAs (rRNAs). Moreover in eukaryotic cells, efficient ribosome maturation requires the transient association of a large number of ribosome biogenesis factors (RBFs) with newly forming ribosomal subunits. Here, we investigated how r-protein assembly events ...

During the assembly process of ribosomal subunits, their structural components, the ribosomal RNAs (rRNAs) and the ribosomal proteins (r-proteins) have to join together in a highly dynamic and defined manner to enable the efficient formation of functional ribosomes. In this work, the assembly of large ribosomal subunit (LSU) r-proteins from the eukaryote S. cerevisiae was systematically investi...

X-ray diffraction patterns of three-dimensional crystals of the large ribosomal subunit from Bacillus stearothemwphilus have been obtained using a synchrotron radiation beam. The patterns contain resolved diffraction spots and indicate packing in relatively small unit cells, the dimensions of which have been tentatively determined. The internal order of the crystals, as reflected in these patte...

The arrival of high resolution crystal structures for the ribosomal subunits opens a new phase of molecular analysis and asks for corresponding analyses of ribosomal function. Here we apply the phosphorothioate technique to dissect tRNA interactions with the ribosome. We demonstrate that a tRNA bound to the P site of non-programmed 70 S ribosomes contacts predominantly the 50 S, as opposed to t...

After the termination step of protein synthesis, a deacylated tRNA and mRNA remain associated with the ribosome. The ribosome-recycling factor (RRF), together with elongation factor G (EF-G), disassembles this posttermination complex into mRNA, tRNA, and the ribosome. We have obtained a three-dimensional cryo-electron microscopic map of a complex of the Escherichia coli 70S ribosome and RRF. We...